User terminal and communication control method

ABSTRACT

A user terminal capable of using an Evolved-UMTS Terrestrial Radio Access Network (E-UTRAN) and a Wireless Local Area Network (WLAN), includes: a storage configured to store a Radio Access Network (RAN) rule for selecting a network, among the E-UTRAN and the WLAN, to be used in a unit of an Access Point Name (APN); a receiver configured to receive an Access Network Discovery and Selection Function (ANDSF) rule for selecting a network, among the E-UTRAN and the WLAN, to be used; and a controller configured to select a selection rule, from among the ANDSF rule and the RAN rule, to be applied to change the network, wherein the controller selects the RAN rule in a case where the user terminal has both the ANDSF rule and the RAN rule and an Inter System Routing Policy (ISRP) is not configured. The ISRP is a function, in the ANDSF rule, for selecting a network, among the E-UTRAN and the WLAN, to be used in a unit of an Internet Protocol (IP) flow.

RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 15/047,289, filed Feb. 18, 2016, which is acontinuation application of international application No.PCT/JP2015/063260, filed May 8, 2015, which claims benefit of U.S.provisional application No. 61/990,918, filed May 9, 2014, the entirecontents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a user terminal used in a cellularcommunication system capable of cooperating with a wireless LAN scheme(WLAN scheme), and relates also to a communication control method.

BACKGROUND ART

In recent years, the use of a user terminal including a cellularcommunication unit and a WLAN communication unit (a so-called dualterminal) is widely spread. Furthermore, the number of WLAN accesspoints (hereinafter briefly referred to as an “access point”) managed byan operator of a cellular communication scheme increases.

To respond to this situation, ANDSF (Access Network Discovery andSelection Function) is being standardized to make efficient an accesspoint discovery process by a user terminal.

Further, in 3GPP (3rd Generation Partnership Project) which is a projectaiming to standardize a cellular communication system, it is planned tostudy a technology enabling strengthening of cooperation in wirelessaccess network (RAN) level between a cellular communication system and aWLAN system (see Non Patent Document 1).

One of the objects of such a technology is to establish a good balanceat a load level between a cellular base station and an access point byimproving the usage of an access point.

In the ANDSF, an ANDSF server arranged in a core network provides a userterminal with information on WLAN by way of a NAS (Non Access Stratum)message. The user terminal selects the cellular base stations and theaccess points on the basis of the information provided from the ANDSFserver to establish a balance at a load level.

Further, the user terminal is notified of a RAN rule set in a cellularRAN. The RAN rule is used to establish a load balance between thecellular base station and the access point in response to an actual loadsituation, etc., of the cellular base station.

PRIOR ART DOCUMENTS Non Patent Document

-   [Non Patent Document 1] 3GPP contribution “RP-1201455”

SUMMARY

According to an embodiment of the present disclosure, a user terminalthat is capable of using an Evolved-UMTS Terrestrial Radio AccessNetwork (E-UTRAN) and a Wireless Local Area Network (WLAN) comprises astorage configured to store a Radio Access Network (RAN) rule forselecting a radio access scheme with Access Point Name (APN)granularity, among the E-UTRAN and the WLAN, and a receiver configuredto receive an Access Network Discovery and Selection Function (ANDSF)rule from the E-UTRAN of the user terminal. The ANDSF rule does notinclude a specific function of selecting the radio access scheme to beused, and a controller is configured to perform a roaming from theE-UTRAN of the user terminal to a visited cellular network, and select aselection rule, from among the ANDSF rule and the RAN rule, to beapplied to change the radio access scheme. In response to the ANDSF rulehaving no specific function for selecting the radio access scheme to beused, the controller selects the RAN rule in a case where the userterminal has both the ANDSF rule and the RAN rule while the userterminal is in the visited cellular network, and the receiver is furtherconfigured to receive assistance information from the visited cellularnetwork, the assistance information used for selecting the radio accessscheme in accordance with the RAN rule. The assistance informationincludes information related to WLAN load information received at thevisited cellular network from the WLAN, and the controller is furtherconfigured to use the assistance information to select the radio accessscheme in accordance with the RAN rule.

According to another embodiment of the disclosure, an apparatus forcontrolling a user terminal capable of using an Evolved-UMTS TerrestrialRadio Access Network (E-UTRAN) and a Wireless Local Area Network (WLAN)comprises a processor configured to store a Radio Access Network (RAN)rule for selecting a radio access scheme with Access Point Name (APN)granularity, among the E-UTRAN and the WLAN, and receive an AccessNetwork Discovery and Selection Function (ANDSF) rule from the E-UTRANof the user terminal, where the ANDSF rule does not include a specificfunction of selecting the radio access scheme to be used, perform aroaming from the E-UTRAN of the user terminal to a visited cellularnetwork, and select a selection rule, from among the ANDSF rule and theRAN rule, to be applied to change the radio access scheme. In responseto the ANDSF rule having no specific function for selecting the radioaccess scheme to be used, the RAN rule is selected in a case where theuser terminal has both the ANDSF rule and the RAN rule while the userterminal is in the visited cellular network. The processor is furtherconfigured to receive assistance information from the visited cellularnetwork, where the assistance information used for selecting the radioaccess scheme is in accordance with the RAN rule, and the assistanceinformation includes information related to WLAN load informationreceived at the visited cellular network from the WLAN. The processor isfurther configured to use the assistance information to select the radioaccess scheme in accordance with the RAN rule.

According to yet another embodiment of the disclosure, a method for auser terminal capable of using an Evolved-UMTS Terrestrial Radio AccessNetwork (E-UTRAN) and a Wireless Local Area Network (WLAN) comprisesstoring a Radio Access Network (RAN) rule for selecting a radio accessscheme, among the E-UTRAN and the WLAN, receiving an Access NetworkDiscovery and Selection Function (ANDSF) rule from the E-UTRAN of theuser terminal, where the ANDSF rule does not include a specific functionof selecting the radio access scheme to be used, performing a roamingfrom the E-UTRAN of the user terminal to a visited cellular network, andselecting a selection rule, from among the ANDSF rule and the RAN rule,to be applied to change the radio access scheme. In response to theANDSF rule having no specific function for selecting the radio accessscheme to be used, the RAN rule is selected in a case where the userterminal has both the ANDSF rule and the RAN rule while the userterminal is in the visited cellular network. The method furthercomprises receiving assistance information from the visited cellularnetwork, the assistance information used for selecting the radio accessscheme in accordance with the RAN rule, where the assistance informationincludes information related to WLAN load information received at thevisited cellular network from the WLAN, and using the assistanceinformation to select the radio access scheme in accordance with the RANrule.

In one embodiment, the controller selects the second selection rule fromamong the first selection rule and the second selection rule, when afunction is not set in the first selection rule, the functiondesignating a radio access scheme to be used.

In one embodiment, the controller selects the selection rule applied tochange the radio access scheme from among the first selection rule andthe second selection rule, on the basis of an area in which the userterminal exists.

In one embodiment, the first selection rule is configured to be set by ahome network of the user terminal. The controller selects the secondselection rule from among the first selection rule and the secondselection rule, when the user terminal is not capable of using the firstselection rule effectively because the user terminal is in roaming.

In one embodiment, the controller selects the second selection rule fromamong the first selection rule and the second selection rule, when theuser terminal is in roaming and the function is not set in the firstselection rule, the function designating a radio access scheme to beused.

In one embodiment, the second selection rule is configured to determinewhether to change a radio access scheme to be used, on the basis of atleast one of load status and radio quality of a radio access schemecurrently used and a candidate of changed radio access scheme.

A user terminal according to one embodiment is capable of using aplurality of radio access schemes including a cellular and a WLAN. Theuser terminal includes: a receiver configured to receive informationindicating whether an offload per APN from the cellular to the WLAN iscapable; a storage configured to store a selection rule which is a ruleapplied in selecting a radio access scheme among the cellular and theWLAN; and a controller configured to determine whether to change a radioaccess scheme to be used for communication with the APN among thecellular and the WLAN on the basis of the information and the selectionrule. The controller switches, from the WLAN to the cellular, a trafficbelonging to an APN indicated by the information which indicates that anoffload is capable.

A user terminal according to one embodiment is capable of using aplurality of radio access schemes including a cellular and a WLAN. Theuser terminal includes: a receiver configured to receive radioassistance information from a cellular base station; and a controllerconfigured to select a radio access scheme by using a radio accessscheme selection rule on the basis of the radio assistance information.The radio assistance information is generated from WLAN load informationacquired from a WLAN node by the cellular base station.

A communication control method according to one embodiment is a methodin a user terminal capable of using a plurality of radio access schemesincluding a cellular and a WLAN. The communication control methodincludes: receiving a first selection rule which is a rule for selectinga radio access scheme to be used among the cellular and the WLAN in aunit of IP flow used in communication with APN; storing a secondselection rule which is a rule for selecting a radio access scheme to beused among the cellular and the WLAN in a unit of the APN; and selectinga selection rule applied to change a radio access scheme from among thefirst selection rule and the second selection rule, when the userterminal has both the first selection rule and the second selectionrule.

A communication control method according to one embodiment is a methodin a user terminal capable of using a plurality of radio access schemesincluding a cellular and a WLAN. The communication control methodincludes: receiving information indicating whether an offload per APNfrom the cellular to the WLAN is capable; storing a selection rule whichis a rule applied in selecting a radio access scheme among the cellularand the WLAN; determining whether to change a radio access scheme to beused for communication with the APN among the cellular and the WLAN onthe basis of the information and the selection rule; and switching, fromthe WLAN to the cellular, a traffic belonging to an APN indicated by theinformation which indicates that an offload is capable.

A communication control method according to one embodiment is a methodin a user terminal capable of using a plurality of radio access schemesincluding a cellular and a WLAN. The communication control methodincludes: receiving radio assistance information from a cellular basestation, the radio assistance information generated from WLAN loadinformation acquired from a WLAN node by the cellular base station; andselecting a radio access scheme by using a radio access scheme selectionrule on the basis of the radio assistance information.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a system configuration diagram according to a first embodimentto a third embodiment.

FIG. 2 is a block diagram of a UE (user terminal) according to the firstembodiment to the third embodiment.

FIG. 3 is a block diagram of an eNB (cellular base station) according tothe first embodiment to the third embodiment.

FIG. 4 is a block diagram of an AP (access point) according to the firstembodiment and the third embodiment.

FIG. 5 is a protocol stack diagram of a radio interface in an LTEsystem.

FIG. 6 is a diagram illustrating an operation environment according tothe first embodiment to the third embodiment.

FIG. 7 is a sequence diagram according to the first embodiment.

FIG. 8 is a system configuration diagram according to the secondembodiment.

FIG. 9 is a system configuration diagram according to the secondembodiment.

FIG. 10 is a flowchart according to the second embodiment.

FIG. 11 is a configuration diagram according to the third embodiment.

DESCRIPTION OF EMBODIMENTS Overview of Embodiments

A user terminal according to a first embodiment is capable of using aplurality of radio access schemes. The user terminal includes: areceiver that receives, from a network, a list in which priority of theradio access scheme to be used is set for each APN; a storage in which aradio access scheme selection rule that is a rule applied when a radioaccess scheme is selected, is stored; and a controller that determineson the basis of the list and the radio access scheme selection rulewhether to change the radio access scheme to be used for connecting withthe APN, and when changing, establishes the connection with the APN viaa target radio access scheme to be changed, wherein when the APN is notlisted in the list, the controller determines whether to change theradio access scheme to be used for the connection with the APN inaccordance with a predetermined condition.

In the first embodiment, the controller may determine whether to switcha connection with the APN that is made via WLAN to a connection that ismade via cellular.

In the first embodiment, the list may describe whether it is possible toswitch the connection to the APN from via cellular to via WLAN.

A user terminal according to a second embodiment is capable of using aplurality of radio access schemes. The user terminal includes: areceiver that receives, from a network, a first selection rule that is arule for selecting the radio access scheme used for each IP flow used incommunication with an APN; a storage that stores a second selection rulethat is a rule for selecting the radio access scheme used for each APN;and a controller that selects the radio access scheme by using the firstselection rule and the second selection rule, and uses the selectedradio access scheme to establish the connection with the APN, whereinthe controller preferentially uses the first selection rule to changethe radio access scheme, and when a predetermined condition issatisfied, the controller does not use the first selection rule and usesthe second selection rule to change the radio access scheme.

In the second embodiment, in the first selection rule, when a functionof designating the radio access scheme to be used is not set, thecontroller may determine that a predetermined condition is satisfied.

In the second embodiment, when a first selection rule is set so that theradio access scheme to be used is selected on the basis of at leasteither one of a time zone and a camp-on location, the controller maydetermine that a predetermined condition is satisfied.

In the second embodiment, the first selection rule is configured to beset by a home network of the user terminal, and when it is not possibleto use the first selection rule as set because the user terminal isroaming, the controller may determine that a predetermined condition issatisfied.

In the second embodiment, the second selection rule may be configured todetermine whether to change the radio access scheme to be used on thebasis of at least either one of a load situation and radio quality of acurrently used radio access scheme and a candidate radio access schemeto be changed.

A user terminal according to a third embodiment is capable of using aplurality of radio access schemes. The terminal includes: a receiverthat receives radio assistance information from a base station of afirst radio access scheme; and a controller that uses a radio accessscheme selection rule set by using the radio assistance information whenthe radio access scheme is selected so as to select a radio accessscheme, wherein the radio assistance information is generated from loadinformation of the second radio access scheme acquired by the basestation of the first radio access scheme from a base station of a secondradio access scheme.

A communication control method according to a first embodiment is amethod in a communication system including a user terminal capable ofusing a plurality of radio access schemes, the user terminal beingconfigured to store a radio access scheme selection rule that is a ruleapplied when a radio access scheme is selected. The communicationcontrol method includes: a step of receiving from a network, by the userterminal, from a network, a list in which priority of the radio accessscheme to be used is set for each APN; a step of determining, by theuser terminal, whether to change the radio access scheme on the basis ofthe list and the radio access scheme selection rule; and a step ofestablishing, by the user terminal, a connection with the APN via atarget radio access scheme to be changed, wherein when the APN is notlisted in the list, the user terminal determines in accordance with apredetermined condition whether to change the radio access scheme to beused.

A communication control method according to a second embodiment is amethod in a communication system including a user terminal capable ofusing a plurality of radio access schemes, the user terminal using afirst selection rule that is a rule for selecting the radio accessscheme to be used for each IP flow used in communication with APN and asecond selection rule that is a rule for selecting the radio accessscheme used for each APN so as to select a radio access scheme, thesecond selection rule being configured to be stored by the userterminal. The communication control method includes: a step ofreceiving, by the user terminal, the first selection rule from anetwork; a step of selecting, by the user terminal, the radio accessscheme by using the first selection rule and the second selection rule;and a step of establishing, by the user terminal, a connection with theAPN by using the selected radio access scheme, wherein the user terminalpreferentially uses the first selection rule to change the radio accessscheme, and when a predetermined condition is satisfied, the userterminal does not use the first selection rule and uses the secondselection rule to change the radio access scheme.

A communication control method according to a third embodiment is amethod in a communication system including a user terminal capable ofusing a plurality of radio access schemes. The method includes: a stepof acquiring, by a base station of a first radio access scheme, loadinformation of a base station of a second radio access scheme from thebase station of the second radio access scheme; a step of generating, bythe base station of the first radio access scheme, radio assistanceinformation from the load information; and a step of notifying, by thebase station of the first radio access scheme, the user terminal of theradio assistance information, wherein the user terminal sets a radioaccess scheme selection rule by using the radio assistance information,and selects the radio access scheme in accordance with the set selectionrule.

First Embodiment

Below, with reference to the drawing, an embodiment will be described inwhich a cellular communication system (LTE system) configured to complywith the 3GPP standards is linked with a wireless LAN (WLAN) system.

(System Configuration)

FIG. 1 is a system configuration diagram according to a firstembodiment. As shown in FIG. 1, a cellular communication system includesa plurality of UEs (User Equipments) 100, an E-UTRAN (Evolved-UMTSTerrestrial Radio Access Network) 10, and an EPC (Evolved Packet Core)20. The E-UTRAN 10 corresponds to a radio access network (RAN). The EPC20 corresponds to a core network.

The UE 100 is a mobile-type radio communication device and performsradio communication with a cell with which a connection is established.The UE 100 corresponds to a user terminal. The UE 100 is a terminal(dual terminal) that supports both communication schemes of cellularcommunication and WLAN communication.

The E-UTRAN 10 includes a plurality of eNBs 200 (evolved Nodes-B). TheeNB 200 corresponds to a cellular base station. The eNB 200 manages oneor a plurality of cells, and performs radio communication with the UE100 with which a connection is established with a cell of the eNB 200.It is noted that the “cell” is used as a term indicating a minimum unitof a radio communication area, and is also used as a term indicating afunction of performing radio communication with the UE 100. Further, theeNB 200 has a radio resource management (RRM) function, a routingfunction of user data, and a measurement control function for mobilitycontrol and scheduling, for example.

The eNBs 200 are connected with one another via an X2 interface.Further, the eNB 200 is connected via an S1 interface to an MME/S-GW 500included in the EPC 20.

The EPC 20 includes a plurality of MMEs (Mobility ManagementEntities)/S-GWs (Serving-Gateways) 500. The MME is a network node thatperforms various mobility controls, etc., on the UE 100, and correspondsto a control station. The S-GW is a network node that performs controlto transfer user data, and corresponds to a switching station.

The WLAN system includes a WLAN access point (hereinafter, brieflyreferred to as “AP”) 300. The WLAN system is configured to comply withvarious IEEE 802.11 specifications, for example. The AP 300 communicateswith the UE 100 in a frequency band (WLAN frequency band) different froma cellular frequency band. The AP 300 is connected, via a router, etc.,to the EPC 20.

Further, in addition to a case where the eNB 200 and the AP 300 areindividually located, the eNB 200 and the AP 300 may also be“Collocated”. As one mode of the “Collocated”, the eNB 200 and the AP300 may be directly connected to each other through any interface of anoperator.

The EPC 20 further includes an ANDSF server 600. The ANDSF server 600manages information on WLAN (hereinafter, referred to as “ANDSFinformation”). The ANDSF server 600 provides the UE 100 with the WLANrelated information by way of a NAS message.

Next, configurations of the UE 100, the eNB 200, and the AP 300 will bedescribed.

FIG. 2 is a block diagram of the UE 100. As shown in FIG. 2, the UE 100includes: antennas 101 and 102; a cellular communication unit 111; aWLAN communication unit 112; a user interface 120; a GNSS (GlobalNavigation Satellite System) receiver 130; a battery 140; a memory 150;and a processor 160. The memory 150 and the processor 160 constitute acontroller. The UE 100 may not have the GNSS receiver 130. Furthermore,the memory 150 may be integrally formed with the processor 160, and thisset (that is, a chipset) may be called a processor 160′.

The antenna 101 and the cellular communication unit 111 are used fortransmitting and receiving a cellular radio signal. The cellularcommunication unit 111 converts a baseband signal output from theprocessor 160 into the cellular radio signal, and transmits the samefrom the antenna 101. Further, the cellular communication unit 111converts the cellular radio signal received by the antenna 101 into thebaseband signal, and outputs the same to the processor 160.

The antenna 102 and the WLAN communication unit 112 are used fortransmitting and receiving a WLAN radio signal. The WLAN communicationunit 112 converts the baseband signal output from the processor 160 intoa WLAN radio signal, and transmits the same from the antenna 102.Further, the WLAN communication unit 112 converts the WLAN radio signalreceived by the antenna 102 into a baseband signal, and outputs the sameto the processor 160.

The user interface 120 is an interface with a user carrying the UE 100,and includes, for example, a display, a microphone, a speaker, andvarious buttons. Upon receipt of the input from a user, the userinterface 120 outputs a signal indicating a content of the input to theprocessor 160. The GNSS receiver 130 receives a GNSS signal in order toobtain location information indicating a geographical location of the UE100, and outputs the received signal to the processor 160. The battery140 accumulates a power to be supplied to each block of the UE 100.

The memory 150 stores a program to be executed by the processor 160 andinformation to be used for a process by the processor 160. The processor160 includes the baseband processor that performs modulation anddemodulation, and encoding and decoding of the baseband signal and a CPUthat performs various processes by executing the program stored in thememory 150. The processor 160 may further include a codec that performsencoding and decoding of sound and video signals. The processor 160implements various processes and various communication protocolsdescribed later.

FIG. 3 is a block diagram of the eNB 200. As shown in FIG. 3, the eNB200 includes an antenna 201, a cellular communication unit 210, anetwork interface 220, a memory 230, and a processor 240. The memory 230and the processor 240 constitute a controller. Furthermore, the memory230 may be integrally formed with the processor 240, and this set (thatis, a chipset) may be called a processor 240′.

The antenna 201 and the cellular communication unit 210 are used fortransmitting and receiving a cellular radio signal. The cellularcommunication unit 210 converts the baseband signal output from theprocessor 240 into the cellular radio signal, and transmits the samefrom the antenna 201. Furthermore, the cellular communication unit 210converts the cellular radio signal received by the antenna 201 into thebaseband signal, and outputs the same to the processor 240.

The network interface 220 is connected to the neighboring eNB 200 via anX2 interface and is connected to the MME/S-GW 500 via the S1 interface.Further, the network interface 220 is used for communication with the AP300 via the EPC 20.

The memory 230 stores a program to be executed by the processor 240 andinformation to be used for a process by the processor 240. The processor240 includes the baseband processor that performs modulation anddemodulation, and encoding and decoding of the baseband signal and a CPUthat performs various processes by executing the program stored in thememory 230. The processor 240 implements various processes and variouscommunication protocols described later.

FIG. 4 is a block diagram of the AP 300. As shown in FIG. 4, the AP 300includes an antenna 301, a WLAN communication unit 311, a networkinterface 320, a memory 330, and a processor 340. Furthermore, thememory 330 may be integrally formed with the processor 340, and this set(that is, a chipset) may be called a processor 340′.

The antenna 301 and the WLAN communication unit 311 are used fortransmitting and receiving the WLAN radio signal. The WLAN communicationunit 311 converts the baseband signal output from the processor 340 intothe WLAN radio signal and transmits the same from the antenna 301.Further, the WLAN communication unit 311 converts the WLAN radio signalreceived by the antenna 301 into the baseband signal and outputs thesame to the processor 340.

The network interface 320 is connected to the EPC 20 via a router, etc.Further, the network interface 320 is used for communication with theeNB 200 via the EPC 20.

The memory 330 stores a program executed by the processor 340 andinformation used for a process by the processor 340. The processor 340includes the baseband processor that performs modulation anddemodulation, and encoding and decoding of the baseband signal and a CPUthat performs various processes by executing the program stored in thememory 330.

FIG. 5 is a protocol stack diagram of a radio interface in the cellularcommunication system. As illustrated in FIG. 5, the radio interfaceprotocol is classified into a layer 1 to a layer 3 of an OSI referencemodel, wherein the layer 1 is a physical (PHY) layer. The layer 2includes a MAC (Media Access Control) layer, an RLC (Radio Link Control)layer, and a PDCP (Packet Data Convergence Protocol) layer. The layer 3includes an RRC (Radio Resource Control) layer.

The PHY layer performs encoding and decoding, modulation anddemodulation, antenna mapping and demapping, and resource mapping anddemapping. Between the PHY layer of the UE 100 and the PHY layer of theeNB 200, data is transmitted via the physical channel.

The MAC layer performs preferential control of data, and aretransmission process and the like by hybrid ARQ (HARQ). Between theMAC layer of the UE 100 and the MAC layer of the eNB 200, data istransmitted via a transport channel. The MAC layer of the eNB 200includes a scheduler for deciding a transport format (a transport blocksize, a modulation and coding scheme, and the like) of an uplink and adownlink, and an assigned resource block.

The RLC layer transmits data to an RLC layer of a reception side byusing the functions of the MAC layer and the PHY layer. Between the RLClayer of the UE 100 and the RLC layer of the eNB 200, data istransmitted via a logical channel.

The PDCP layer performs header compression and decompression, andencryption and decryption.

The RRC layer is defined only in a control plane. Between the RRC layerof the UE 100 and the RRC layer of the eNB 200, a control message (anRRC message) for various types of setting is transmitted. The RRC layercontrols the logical channel, the transport channel, and the physicalchannel in response to establishment, re-establishment, and release of aradio bearer. When there is a connection (RRC connection) between theRRC of the UE 100 and the RRC of the eNB 200, the UE 100 is in aconnected state (RRC connected state), and otherwise, the UE 100 is inan idle state (RRC idle state).

A NAS (Non-Access Stratum) layer positioned above the RRC layer performssession management or mobility management, for example. The MME 300 andthe ANDSF server 600 exchange NAS massages with the UE 100.

Operation According to First Embodiment

Next, an operation according to the first embodiment will be described.

(1) Operation Environment

FIG. 6 is a diagram illustrating an operation environment according tothe first embodiment. As shown in FIG. 6, a plurality of APs 300 areprovided in a coverage of the eNB 200. Each of the plurality of APs 300are an AP (Operator controlled AP) managed by an operator.

Further, a plurality of UEs 100 are located in the coverage of the eNB200 and in the coverage of the AP 300. The UE 100 establishes aconnection with the eNB 200, and performs cellular communication withthe eNB 200. Specifically, the UE 100 exchanges a cellular radio signalincluding a traffic (user data) with the eNB 200. Alternatively, someUEs 100 may not establish a connection with the eNB 200.

When the eNB 200 establishes a connection with a large number of UEs100, a load level of the eNB 200 increases. The “load level” means thedegree of congestion in the eNB 200 such as a traffic load of the eNB200 or usage of radio resources of the eNB 200. Here, when the exchangeof traffic between the eNB 200 and the UE 100 is switched to theexchange of traffic between the AP 300 and the UE 100, it becomespossible to transfer (offload) the traffic load in the eNB 200 to the AP300.

However, in order to keep the UE 100 to be in a state of being able toconnect with the AP 300, it is necessary that the WLAN communicationunit 112 of the UE 100 is constantly in the on state to continue an APdiscovery process, resulting in an increase in power to be consumed inthe UE 100. Therefore, when the information on the AP 300 is provided tothe UE 100, it becomes possible to make efficient the AP discoveryprocess performed by the UE 100 and restrain an increase in power to beconsumed in the UE 100.

(2) Operation Content

When the UE 100 is offloaded from the eNB 200 to the AP 300, the UE 100determines whether it is possible to be offloaded for each externalconnection-target network (APN: Access Point Name). An Offload-able APNlist, which is information for determining whether it is possible to beoffloaded for each APN, is notified from the network to the UE 100.Specifically, the list is notified from a network function such as theMME 500.

Here, whether it is possible to be offloaded in an APN not included inthe Offload-able APN list is determined by the UE 100.

Specifically, the UE 100 according to the present embodiment can beconnected to a plurality of radio access schemes, and includes: areceiver (processor 160 and cellular communication unit 111) thatreceives, from a network, an Offload-able APN list, which is a list towhich priority of a radio access scheme to be used is set for each APN;a storage (memory 150) in which a RAN rule, which is a rule applied whena radio access scheme is selected, is stored; and a controller(processor 160) that determines, on the basis of the Offload-able APNlist and the RAN rule, whether to change the radio access scheme to beused for connecting to the APN between cellular and WLAN, and whenchanging, establishes the connection with the APN via a target radioaccess scheme to be changed. When an APN is not listed in theOffload-able APN list, the controller determines whether to change theradio access scheme to be used for the connection with the APN inaccordance with a predetermined condition.

Here, the RAN rule describes whether RSRP, RSRQ, a communication speed,a load situation, etc., of the used radio access scheme satisfy apreviously configured condition. This is a rule where when the loadsituation of the eNB 200 is larger than a threshold value set in the RANrule, for example, the radio access scheme is changed to WLAN.

Further, examples of the predetermined condition include: a conditionthat the UE 100 does not make a change to the WLAN when an APN to whichconnection can be made only when the cellular is used is concerned; acondition that the UE 100 determines a change from load situations ofthe cellular and the WLAN when an APN not dependent upon the radioaccess scheme is concerned; and a condition of in the process of movingor standing still.

By using FIG. 7, an operation sequence according to the presentembodiment will be described.

The UE 100 receives the Offload-able APN list from the MME 500 (S701).

Further, the UE 100 receives RAN level assistance information (RANAssistance Parameter) used for setting a condition of a RAN rule, fromthe eNB/RNC 200 (S702).

Here, communication is under progress with an APN1 by using the cellular(S703 Traffic which belongs to APN1). It is noted that the APN1 isincluded in the Offload-able APN list.

By using the RAN rule, the UE 100 determines to change the used radioaccess scheme of the APN1 included in the Offload-able APN list in orderto be offloaded from the cellular to the WLAN (S704: Steer traffic toWLAN according to RAN rule and offload-able APN list).

The UE 100 changes the radio access scheme to be used for connecting tothe APN1, from the cellular to the WLAN. Further, the UE 100 connects toan APN2 by using the WLAN. Here, the APN2 is not included in theOffload-able APN list (S705).

The UE 100 receives again a RAN Assistance Parameter from the eNB/RNC200 (S706). On the basis of the received RAN Assistance Parameter, theRAN rule is reset.

Here, the RAN Assistance Parameter is generated on the basis of a radiosituation of the eNB/RNC 200, and thus, when the RAN rule is set whilethe radio situation is reflected.

The UE 100 determines on the basis of the RAN rule to steer the trafficof the APN1 back to the cellular (S707: RAN rule is satisfied and the UEdecides to steer APN1 traffic back). For example, when the load of thecellular decreases, the UE 100 determines to steer the traffic of theAPN1 back to the cellular.

The UE 100 changes the radio access scheme used for connection to theAPN1, from the WLAN to the cellular (S708: Steer traffic from WLANaccording to RAN rule and offloadable APN list). As a result, when theUE 100 intends to establish a connection to the APN1, the UE 100 usesthe WLAN (S709).

On the other hand, the UE 100 determines whether the APN2 not includedin the Offload-able APN list complies with a predetermined condition,and selects to continue the communication by using the WLAN (S710). Forexample, the UE 100 compares throughput of the WLAN with that of thecellular, and when the WLAN is higher, the UE 100 continues to use theWLAN.

According to the present embodiment, it is possible to select the radioaccess scheme to be used by using the Offload-able APN list, and whenthe APN not included in the Offload-able APN list is concerned, the UE100 is capable of using a suitable radio access scheme by selecting theradio access scheme to be used.

Second Embodiment

By using FIG. 8 to FIG. 10, a second embodiment will be described. It isnoted that a description of parts overlapping the first embodiment willbe not be provided, and a difference from the first embodiment will bemainly described.

As shown in FIG. 8, the UE 100 according to the present embodimentdetermines which to use the WLAN or the cellular in radio access scheme,from the ANDSF received from the network and the RAN rule stored in theUE 100.

Here, the ANDSF is transmitted from an ANDSF server deployed in anetwork. The ANDSF includes ISRP (Inter System Routing Policy) which isinformation on a routing policy between systems. In the ISRP, it ispossible to set a radio access scheme used for each IP flow.

On the other hand, the RAN rule is a rule for selecting a radio accessscheme used for each APN, and is set on the basis of a radio situationsuch as a load of a radio access scheme, and thus, the UE 100 is capableof selecting the most appropriate radio access scheme in response to theradio situation.

For example, as shown in FIG. 9, the UE 100 uses the ANDSF or the RANrule to change the connection to an APN #1 from the WLAN to the cellular(901 to 902), and is capable of continuously using the WLAN to an APN #2(903).

Further, when the ISRP included in the ANDSF is used, it is possible touse a radio access scheme different from IP flows even when theconnection to the same APN is concerned.

In a conventional scheme, when the UE 100 holds the ANDSF and the RANrule, a method of applying the two rules is not regulated, and there isa concern that it is not possible to appropriately select the radioaccess scheme.

In the present embodiment, the RAN rule is applied when a predeterminedcondition is satisfied, while the UE 100 preferentially applies theANDSF.

Specifically, the UE 100 can be connected to a plurality of radio accessschemes, and includes: a receiver (cellular communication unit 111 andprocessor 160) that receives ANDSF from a network; a storage (memory150) in which a RAN rule is stored; and a controller (processor 160)that selects either one of cellular or WLAN from the ANDSF and the RANrule and uses the selected radio access scheme to establish a connectionwith the APN. The controller preferentially uses the ANDSF to change theradio access scheme; when a predetermined condition is satisfied, thecontroller changes the radio access scheme on the basis of the RAN rulewithout using the ANDSF.

Here, in the ANDSF, when a function itself of specifying a radio accessscheme to be used is not set, and/or it is not possible to select aradio access scheme because some functions are set inactive, the UE 100may determine that the predetermined condition is satisfied. The UE 100selects the access scheme to be used by using the RAN rule.

Further, when the ANDSF is set so that a radio access scheme to be usedis selected on the basis of at least either one of a time zone and acamp-on location, the UE 100 may determine that the predeterminedcondition is satisfied.

For example, in a time zone or a camp-on location (urban area) wherecellular traffic is large, even when the setting in which the WLAN ispreferentially used is the ANDSF, the actual cellular traffic may besmall. In this case, the UE 100 more preferably selects a radio accessscheme by using the RAN rule set by using RAN level assistanceinformation, which is an actual radio situation.

It is noted that the RAN rule is configured so that the most appropriateradio access scheme is selected on the basis of a cellular of a radioaccess scheme to be selected, a load situation of WLAN, and radioquality.

Further, normally the ANDSF is configured to be set by a home network(HPLMN) of the UE 100. On the other hand, the RAN level assistanceinformation for setting the RAN rule is notified from the eNB 200 inwhich the UE 100 exists. When the UE 100 is roaming, it is preferablethat a radio access scheme is selected by using the RAN rule designatedby the eNB 200 in which the UE 100 exists, rather than using the ANDSFset by the HPLMN.

Thus, when the UE 100 is roaming, the UE 100 may determine that thepredetermined condition is satisfied.

By using FIG. 10, a determination flow when the ANDSF and the RAN ruleare applied will be described.

The UE 100 selects the radio access scheme for each APN or for each IPflow in the APN.

The UE 100 determines for the APN or the APN flow to be determinedwhether a valid ANDSF is set (S1000). Here, the “valid ANDSF” applieswhen the above-described predetermined condition is not satisfied.

When the ANDSF is valid, the UE 100 uses the ANDSF to select which touse, as a radio access scheme, WLAN or cellular (S1001).

On the other hand, when the ANDSF is invalid, the UE uses the RAN ruleto select to use either one of the radio access schemes (S1002).

As described above, according to the embodiment-based disclosure, the UE100 is capable of appropriately selecting a radio access scheme when theUE 100 holds the ANDSF and the RAN rule.

Third Embodiment

By using FIG. 11, a third embodiment will be described. It is noted thata description of parts overlapping the first and second embodiments willbe not be provided, and a difference from the first and secondembodiments will be mainly described.

In a RAN rule according to the present embodiment, the eNB 200 does notgenerate the RAN level assistance information only from a radiosituation of a cell managed by the eNB 200, but generates the RAN levelassistance information also in consideration of a load situation of theAP 300 that may be selected.

More specifically, when the eNB 200 acquires load information of the AP300, the eNB 200 generates the RAN level assistance information from theload information. The eNB 200 notifies the user terminal of thegenerated RAN level assistance information. The UE 100 uses the RANlevel radio assistance information to set the RAN rule, and inaccordance with the set selection rule, selects the radio access scheme.

Further, the UE 100 according to the present embodiment is characterizedby including: a receiver (cellular communication unit 111 and processor160) that receives RAN level assistance information; and a controller(processor 160) that selects a radio access scheme from the RAN levelassistance information, wherein the RAN level assistance information isgenerated from load information of the AP 300 acquired by the eNB 200from the AP 300, and the controller selects the radio access scheme onthe basis of the set radio access scheme selection rule.

Here, the eNB 200 may directly acquire, from the AP 300, the loadinformation of the AP 300, and may indirectly acquire the loadinformation via a network device.

By using FIG. 11, an operation flow according to the present embodimentwill be described.

The eNB 200 acquires the load information of the AP 300, from the AP 300(S1100).

It is noted that when the type of cellular is not LTE (EUTRAN) but 3G(UTRAN), RNC acquires the load information of the AP 300.

The eNB 200 generates the RAN level assistance information from theacquired load information of the AP 300, and notifies the UE 100 thereof(S1101).

The UE 100 sets the RAN rule by using the notified RAN level assistanceinformation, and selects a radio access scheme. Specifically, the UE 100determines whether or change the radio access scheme to be used, fromthe LTE to the WLAN.

Other Embodiments

The above-described first embodiment to third embodiment may beperformed separately and independently and may also be performed througha combination thereof.

In the above-described embodiments, as one example of a cellularcommunication scheme, the LTE scheme is described; however, the presentdisclosure is not limited to the LTE scheme, and the present disclosuremay be applied to schemes other than the LTE scheme.

Further, as an example of a radio access scheme other than the cellularcommunication scheme, the WLAN is described; however, the presentdisclosure is not limited to the WLAN and may of course be applied to aradio access scheme such as WiMAX.

APPENDIX 1

Below, the additional notes of the embodiments will be described.

(1. Introduction)

In the previous meeting, SA2 informed RAN2 of its decision for trafficrouting from RAN to WLAN without ANDSF, i.e. the MME/SGSN indicates tothe UE in NAS signalling which APNs must not be offloaded oralternatively which APNs may be offloaded to WLAN. However granularityof traffic routing from WLAN to RAN is still unclear. This appendixoffers several alternatives for traffic routing from WLAN to RAN withoutANDSF case with various level of granularities.

(2. Discussion)

(2.1. Traffic Routing from WLAN to RAN Using RAN Rule)

If UE applies ANDSF functions, traffic routing from WLAN to RAN isalready clear. For example, ISMP capable UE would steer all trafficsfrom WLAN to RAN, while ISRP capable UE may steer traffics at the IPflow level depending on what is defined in the ANDSF functions. However,if ANDSF is unavailable to the UE, and RAN rules is applied, it has notbeen decided how traffic should be steered from WLAN to RAN and whetherthe decision should be based on RAN rules. This issue may also beapplicable for the case when the UE is provisioned with both RAN rulesand ANDSF but none of the available ANDSF rules are valid, since thiscase is still FFS according to SA2.

The understanding is that the access stratum in the UE shall indicate tothe upper layers when RAN specified conditions are satisfied for a timeinterval TsteeringWLAN. For traffic routing from RAN to WLAN, it isalready agreed that the MME indicates to the UE via NAS signallingwhether the traffic is offload-able or not. However, for traffic routingfrom WLAN to RAN, there is the possibility that the UE may not be ableto receive NAS signalling. Therefore, it is still unclear whether it isnecessary for the network to specify (based on APN) which traffic shouldbe steered back to 3GPP and whether it is necessary for the UE to havethe most up-to-date traffic steering information from the network.

The following three alternatives should be considered for trafficrouting from WLAN to RAN.

-   -   Alt.1: UE steers all traffics from WLAN to RAN.

This is the simplest alternative. Once the RAN specified rule issatisfied for traffic routing from WLAN to 3GPP, the UE will steer alltraffic to RAN. This alternative also reduces the UE's power consumptionsince the UE does not need to be connected to both RAN and WLANsimultaneously.

-   -   Alt.2: Traffic selected to be steered to RAN is up to UE        implementation.

With this alternative, there is no need to define traffic to be steeredwith RAN rules. However, it is still necessary for the RAN rule to besatisfied for traffic steering from WLAN to RAN before the UE is allowedto steer any traffic to RAN.

If this alternative is agreed, the statement “UE behaviour is up to UEimplementation in the direction from WLAN to 3GPP RAN” may be describedin Stage 2.

-   -   Alt.3 UE steers traffic from WLAN to RAN according to        offloadable APN list.

UE steers traffic back to 3GPP, which once belonged to offloadable APN.For example, the following steps may be applied for the selection oftraffic to be steered to RAN.

a) The network entity (e.g. MME, P-GW) specifies a subset of alloffloadable APNs to be steered from WLAN to RAN.

b) UE steers traffic to RAN based on the specified APNs as long as theRAN rule is satisfied. It is assumed that all traffic belonging to thespecified APNs are steered back.

c) For the remaining traffic not mapped to any of the specified APNs,the UE may decide autonomously whether they should be steered to theRAN.

The only difference between Alt 3 and what is already specified for thetraffic steering from RAN to WLAN is that the UE also gets to decidewhether the remaining traffic not on the APN list should be steered toRAN.

It may be assumed that the APN list isn't changed frequently, so it maybe considered semi-static. In general, the offloadable APN list can bedifferent for each traffic steering direction, i.e. MME can provide bothoffloadable APN list from RAN to WLAN and offloadable APN list from WLANto RAN. However it is questionable if there is any benefit todistinguish the APN lists. In comparison, Alt 1 provides an easysolution. It is testable, and it isn't necessary for the UE to beconnected to both RAN and WLAN simultaneously. Alt 2 provides moreflexibility to the UE, but this functionality cannot be verified throughtesting. Although Alt 3 provides the RAN full control of trafficsteering in both directions, it is also the most complicated of all thealternatives.

Considering the pros and cons of the three alternatives, Alt.1 appearsto provide the most reasonable compromise.

Proposal 1: UE shall steer all traffics from WLAN to RAN when RANspecified rules are satisfied.

(3. Conclusion)

This contribution discusses and clarifies traffic routing with RAN rulesin the direction from WLAN to RAN.

APPENDIX 2

(1. Introduction)

The way forward on Multi-RAT Joint coordination was agreed as follows

1. General requirements and definitions for Traffic Steering andSpectrum re-allocation definition

2. Use cases for Coordination Involving 3GPP/WLAN

The further discussion on 3GPP/WIFI interworking will be based onfollowing steps.

1) identify the potential scenarios/use cases;

2) investigate what information needed;

3) define the way to obtain the information.

It is noted that the discussion should regard to RAN2/SA2 works.

On the basis of agreed discussion steps, this paper provides additionalscenarios/use cases identified as the step 1.

(2. Additional Scenarios/Use Cases Involving WLAN)

(2.1. Current Potential Use Cases)

At the last meeting, potential use cases were discussed and the minutescaptured the following texts;

Use Cases:

1: Seamless mobility from WLAN to 3GPP: mobility without serviceinterruption, any SA2 work on service continuity?

2: Appropriate UE steering from WLAN to 3GPP

3: Resolving mobility decision conflict

4: Automatic WLAN AP/AC parameters collection/setting

In the following sections, we would propose additional scenarios/usecases.

(2.2. 3GPP/WLAN Radio Interworking Complement Scenario)

In this section we provide some possible use cases to complement themechanism in 3GPP/WLAN Radio Interworking WI discussed in RAN2.

(2.2.1. Network Selection/Traffic Enhancements)

At RAN2 #85-bis meeting, it was agreed that the actual decision ofoffloading can be determined by a single set of RAN assistanceparameters provided by the eNB/NB.

Agreements

1. For the RAN mechanism a single set of RAN rules with one set of RANassistance parameters that determines access selection and trafficrouting. It is up to the UE whether it associates with the Access Pointonly when the rule is met or already before. If multiple WLANs meet thecriteria, it is up to the UE implementation which one to choose (orfollow the absolute priorities if such are considered necessary andsignalled (FFS)).

Observation 1: eNB/NB has to configure RAN assistance parameters used inRAN rules to determine network selection/traffic steering to/from WLAN.

Obviously, the role of eNB/NB should be to provide precise RANassistance parameters for the appropriate decision of access networkand/or traffic steering. In the case, a possible problem is, how theeNB/NB decides suitable RAN assistance parameters, taking into accountcurrent loads in eNB/NB and WLAN APs. The eNB/NB should have thecapability to gather information, e.g. load information and/or maximumachievable data rate, from WLAN AP or AC, in order to adjust RANassistance parameters before signalling to the UE, e.g. comparing bothown load and WLAN load.

Proposal 1: RAN3 should consider the precise control of networkselection/traffic steering use case to facilitate eNB/NB to adjust RANassistance parameters signalled to the UE.

Proposal 2: If Proposal 1 is acceptable, RAN3 should discuss the methodfor the eNB/NB to obtain at least load information and maximumachievable data rate from WLAN AP/AC.

(2.2.2. Offloading Granularity)

We analyzed that RAN3 may enhance the granularity of traffic steering inthe RAN solution because RAN2 agreed as follows;

Agreements

2. RAN solution without ANDSF supports APN level offload granularityonly. [ . . . ]

Currently the RAN solution provided by RAN2 may be consideredsuboptimal, since it's common view that smaller granularity of trafficsteering can bring more gains in WLAN interworking, from perspective ofe.g. load balancing between 3GPP RAN and WLAN.

Comparing to Core Network solutions from granularity point of view,MAPCON (Multi Access PDN Connectivity) can be similar with APN leveloffload above. However, RAN solution does not have the capability for IPflow level offloading, while CN has IFOM (IP Flow Mobility) to supportit. On the other hand, RAN has the knowledge of a bearer, so RAN can usethe information for bearer level steering which has not been provided byCN. Therefore, RAN 3 should consider enhancing the steering granularityof the RAN solution in discussed in RAN2.

Observation 2: The current RAN solution has a limitation in terms ofsteering granularity.

Observation 3: There are four steering granularities, per-IP flow,per-bearer, per-APN and per-UE in precision order, while RAN2 solutionhas just per-APN steering.

Proposal 3: RAN3 should consider the steering granularity enhancementsuse case to facilitate flexible traffic steering.

If Proposal 3 is acceptable, we should consider the direction of thetraffic steering, i.e. from 3GPP RAN to WLAN and from WLAN to 3GPP.

In case traffic is offloaded from 3GPP RAN to WLAN, it may be desirablefor the eNB/NB to obtain the QoS control capability of specific WLANAP/AC in order for the eNB/NB to decide whether GBR traffic, e.g. VoIPand/or video streaming, can be offloaded to WLAN or not. As is wellknown, today's WLAN has the optional capability of QoS control as IEEE802.11e. If the option in WLAN can be assumed, the eNB/NB will performthe traffic steering more efficiently without degradation to the currentcarrier-grade level QoS.

Observation 4: For offloading from RAN to WLAN, the QoS controlcapability of specific WLAN AP/AC should be provided to the RAN.

As for the onloading case, i.e. traffic steering from WLAN to 3GPP RAN,the QoS characteristics of the selected traffic may be useful to map theWLAN traffic into 3GPP traffic in the eNB/NB.

Observation 5: For onloading from WLAN to RAN, the QoS characteristicsof the selected traffic to be steered should be provided to the RAN.

(2.3. WLAN AP Deployment)

A practical multi-RAT deployment was introduced in the contribution inRAN2. According to the contribution, tens of APs are deployed per 3GPPcell in average, while it may be hundreds of APs assuming non-uniformdeployment, e.g. in dense urban. For some time in the future the numberis expected to be increased, so it may surpass the assumption for H(e)NBdeployment.

Observation 6: The number of WLAN APs can be substantial and will onlyincrease significantly over time.

It is also expected that signalling load in a network and/or processingload in a control node will become an issue for Multi-RAT jointcoordination involving WLAN, similar to the H(e)NB case.

Proposal 4: Signalling and processing load should be considered for theuse case with large number of WLAN AP deployment.

(2.4. 3GPP Level Security Over WLAN)

Currently, traffic which is initiated in 3GPP network is often offloadedto WLAN network including trusted WLAN access and untrusted WLAN access,where the untrusted WLAN access does not ensure security. 3GPP CN hasdeveloped a solution defining ePDG (Evolved Packet Data Gateway) tofacilitate that the UE establishes a secure tunnel, i.e. IPsec, beforethe traffic routing. However, from RAN's perspective, it cannot directlycontrol the security of the traffic to be steered and it may beinefficient for the tunneling to be established whenever trafficsteering to WLAN is needed. Therefore, a more flexible security solutionfor RAN should be discussed in this SI.

Proposal 5: RAN3 is asked to discuss whether untrusted WLAN should behandled or not.

Clearly, other modifications and manners of practicing this inventionwill occur readily to those of ordinary skill in the art in view ofthese teachings. The above description is illustrative and notrestrictive. This invention is to be limited only by the followingclaims, which include all such modifications and manners of practicewhen viewed in conjunction with the above specification and accompanyingdrawings. The scope of the invention should, therefore, be determinednot with reference to the above description, but instead should bedetermined with reference to the appended claims along with their fullscope of equivalents.

INDUSTRIAL APPLICABILITY

The present disclosure is useful for communication fields.

The invention claimed is:
 1. A user terminal capable of using anEvolved-UMTS Terrestrial Radio Access Network (E-UTRAN) and a WirelessLocal Area Network (WLAN), comprising: a storage configured to store aRadio Access Network (RAN) rule for selecting a radio access scheme withAccess Point Name (APN) granularity, among the E-UTRAN and the WLAN; areceiver configured to receive an Access Network Discovery and SelectionFunction (ANDSF) rule from the E-UTRAN of the user terminal, wherein theANDSF rule does not include a specific function of selecting the radioaccess scheme to be used; and a controller configured to perform aroaming from the E-UTRAN of the user terminal to a visited cellularnetwork, and select a selection rule, from among the ANDSF rule and theRAN rule, to be applied to change the radio access scheme, wherein inresponse to the ANDSF rule having no specific function for selecting theradio access scheme to be used, the controller selects the RAN rule in acase where the user terminal has both the ANDSF rule and the RAN rulewhile the user terminal is in the visited cellular network, and thereceiver is further configured to receive assistance information fromthe visited cellular network, the assistance information used forselecting the radio access scheme in accordance with the RAN rule,wherein the assistance information includes information related to WLANload information received at the visited cellular network from the WLAN,and the controller is further configured to use the assistanceinformation to select the radio access scheme in accordance with the RANrule.
 2. An apparatus for controlling a user terminal capable of usingan Evolved-UMTS Terrestrial Radio Access Network (E-UTRAN) and aWireless Local Area Network (WLAN), the apparatus comprising: processorconfigured to store a Radio Access Network (RAN) rule for selecting aradio access scheme with Access Point Name (APN) granularity, among theE-UTRAN and the WLAN; receive an Access Network Discovery and SelectionFunction (ANDSF) rule from the E-UTRAN of the user terminal, wherein theANDSF rule does not include a specific function of selecting the radioaccess scheme to be used; perform a roaming from the E-UTRAN of the userterminal to a visited cellular network, and select a selection rule,from among the ANDSF rule and the RAN rule, to be applied to change theradio access scheme, wherein in response to the ANDSF rule having nospecific function for selecting the radio access scheme to be used, theRAN rule is selected in a case where the user terminal has both theANDSF rule and the RAN rule while the user terminal is in the visitedcellular network, and the processor is further configured to receiveassistance information from the visited cellular network, the assistanceinformation used for selecting the radio access scheme in accordancewith the RAN rule, wherein the assistance information includesinformation related to WLAN load information received at the visitedcellular network from the WLAN, and use the assistance information toselect the radio access scheme in accordance with the RAN rule.
 3. Amethod for a user terminal capable of using an Evolved-UMTS TerrestrialRadio Access Network (E-UTRAN) and a Wireless Local Area Network (WLAN),comprising: storing a Radio Access Network (RAN) rule for selecting aradio access scheme, among the E-UTRAN and the WLAN; receiving an AccessNetwork Discovery and Selection Function (ANDSF) rule from the E-UTRANof the user terminal, wherein the ANDSF rule does not include a specificfunction of selecting the radio access scheme to be used; performing aroaming from the E-UTRAN of the user terminal to a visited cellularnetwork, and selecting a selection rule, from among the ANDSF rule andthe RAN rule, to be applied to change the radio access scheme, whereinin response to the ANDSF rule having no specific function for selectingthe radio access scheme to be used, the RAN rule is selected in a casewhere the user terminal has both the ANDSF rule and the RAN rule whilethe user terminal is in the visited cellular network, and the methodfurther comprises: receiving assistance information from the visitedcellular network, the assistance information used for selecting theradio access scheme in accordance with the RAN rule, wherein theassistance information includes information related to WLAN loadinformation received at the visited cellular network from the WLAN; andusing the assistance information to select the radio access scheme inaccordance with the RAN rule.